Part of the logic on how that is easy to apply is based on the fact that we also have a gas pickup. The gas pickup gives us the security blanket to let the EV's charge get down lower and lower if it rains multiple days in a row, hoping to get a sunny day to charge the EV for free. If we make a mistake and wake up one morning saying, "Oh, wait. I have a lot more driving to do today than I thought. I wish I had charged the EV even if it meant adding to our power bill." No problem. The gas pickup is available.
Thus, we allow ourselves to go without a charge longer, and longer. In the end, we don't let the EV get below 100 miles range. So a max of 230 mile range (if it's charged to 80% and we're not doing highway driving) minus 100 miles before we charge on the grid, means 130 miles of driving. That almost always results in a sunny free power day to charge it to 80% before we reach that point.
If you can make your transportation and your HVAC and your water heater all result in having to buy less energy, then you've won the major battles in cutting your energy costs. Bonus points if you can do so without changing your lifestyle (i.e. drive less, set the HVAC temp to lower in the winter or higher in the summer than you want, etc.) That's the main reason we got an EV and do most of our driving in it. We can't make our own gasoline, but we can make our own power.
We have a geothermal heating and cooling system. It works beautifully and economically. We also have a large Vermont Casting wood stove and burn a couple cords of firewood each fall, winter and early spring. So our heating and cooling costs are pretty low. What I would like to do is a bank of solar panels which would charge batteries capable of powering the house for a few days since we have a lot of power failures here in north western N.J. All of our ash trees are dead (ash borers) and falling across power lines when a typical thunderstorm hits, and power is out, could be for a few hours or days. Gas powered generators are ok for a while, but get old soon. A whole house generator (Generac) is costly for the time you need it. We have a couple acres so we don’t have to have roof mounted solar. I haven’t researched all of the costs yet, but I’ll get there eventually.